1. Field of the Invention
The present invention relates to a new copolymer of an aliphatic polycyclic monomer having an alpha, beta-unsaturated nitrile with a certain copolymerizable monomer, and particularly, to copolymers of 1-(1'-cyanoethenyl)adamantane or 2-norbornene-2-carbonitrile with an acrylate or methacrylate derivative. These copolymers would be used as functional polymer materials for various electrical, optical, and medical uses.
The invention also relates to resist compositions of the chemical amplification type comprising the copolymer of the invention and a photo acid generator. These compositions are advantageously used as resist materials particularly in the production of highly integrated semiconductor devices.
The invention further relates to 1-(1'-cyanoethenyl)adamantane which is a novel compound and is used as the starting material for the copolymer. In addition, this novel compound may be used as a starting material for synthesis of various organic compounds and polymers.
2. Description of the Related Art
Certain compounds having an adamantane skeleton and a substituent containing a polymerizable double bond are known. These compounds include, e.g., 1-vinyladamantane and 1-isopropenyladamantane. The only known polymer materials obtained from such known adamantane compounds are homopolymers produced using a cationic catalyst such as aluminum bromide (Miljenko Zuanic et al., J.Polym. Sci., Polym. Lett. Ed., 19,387 (1981)), and radical copolymers of such an adamantane compound with maleic anhydride or maleimide having a double bond of very low electron density.
For unsaturated compounds having a norbornene skeleton, many compounds are known, including, e.g., norbornylene and 5-vinyl-2-norbornene. Also, many polymers are known which use such known norbornene compounds as a main moiety. However, copolymers of 2-norbornene-2-carbonitrile and an acrylate or methacrylate derivative according to the present invention are not known. Further, with 1,2-substituted olefinic compounds such as norbornylene, the only polymers which are known are obtained by ring opening polymerization through a Lewis acid catalyst such as titanium tetrachloride, and which are copolymers obtained by radical polymerization of such a compound with maleic anhydride or maleimide having a double bond of very low electron density.
Thus, both prior adamantane compounds and norbornene compounds can provide limited copolymers such as those delineated above, but cannot provide other copolymers such as those obtained by polymerization between an adamantane or norbornene compound and a monomer having wider uses such as an acrylic or methacrylic compound. The prior adamantane and norbornene compounds therefore make it difficult to modify copolymerized materials so as to attain desired properties.
For example, when the prior copolymers are applied to photoresist materials used for a photolithographic process in the manufacture of semiconductor devices, the copolymers have disadvantages and are difficult to process into a thin film due to the hardness of the copolymer, and thus prevent the production of a fine resist pattern due to their high absorption of far ultraviolet rays. Advanced photolithographic processes used in the semiconductor device manufacture particularly require photoresist materials showing high transparency to shorter wavelength radiation, such as far ultraviolet rays, so as to allow the production of more and more highly integrated devices. It would therefore be beneficial to the art of manufacture of highly integrated semiconductor devices, to provide a resist material having excellent properties from which finer resist films can be obtained.
To the inventor's knowledge, the adamantane compound of 1-(1'-cyanoethenyl)adamantane, which may be used a starting material for the copolymers of the invention, was not known prior to the present invention.